Optical glass

ABSTRACT

An optical glass with high refractive index and low dispersion, having refractive index nd of 1.78-1.95, Abbe number νd of 32-50, and contains no GeO2, so it is not easily devitrified. An optical glass, represented by cation %, including: 1-20% of Si4+; 25-60% of B3+; 10-40% of La3+; 0-15% of Y3+; 0-20% of Nb5+; 0-15% of Ti4+; 0-10% of Ta5+; 0-5% of W6+; 0-15% of Zr4+; 0-10% of Zn2+; 0-10% of Bi3+. An optical glass with excellent transmittance, an optical glass preform and an optical element formed by the above optical glass. The optical element made by the above optical glass and the above glass preform or optical element blank, such as lens, can be used for optical systems.

TECHNICAL FIELD

The invention relates to an optical glass with high refractive index and low dispersion, and press-molding glass preform and an optical element formed by the above glass.

BACKGROUND

The optical glass with high refractive index and low dispersion can correct chromatic aberration to miniaturize the optical system, thus it is developed rapidly in recent years. Particularly the market demands on the optical glass with high refractive index and low dispersion, having refractive index nd of 1.78-1.95 and Abbe number vd of 32-50, are increasing.

The formulation system often used for such optical glass is lanthanum borate glass system, but the content of B₂O₃ and SiO₂ as network formers is higher, the refractive index nd of the optical glass may be reduced; but if more ingredients with high refractive index are given to glass in the formulation system, it is very easy to cause the glass stability to be reduced and the glass devitrified in the manufacturing process. Meanwhile, low-cost glass is the direction of improving glass in recent years, and the cost of the raw material GeO₂ usually introduced in the previous manufacturing is higher.

SUMMARY

The technical problem to be resolved in the present invention is to provide an optical glass with high refractive index and low dispersion, having refractive index nd of 1.78-1.95, Abbe number vd of 32-50, and the glass contains no GeO₂, so it is not easily devitrified.

The present invention also provides a glass preform and an optical element formed by the above optical glass.

To solve the technical problem, the technical scheme of the present invention provides: an optical glass, represented by cation %, comprising:

1-20% of Si⁴⁺;

25-60% of B³⁺;

moreover, the total amount of Si⁴⁺ and B³⁺ being 30-70%;

10-40% of La³⁺;

0-15% of Y³⁺;

the total amount of La³⁺, Y³⁺, Gd³⁺ and Yb³⁺ is 20-55%;

(Si⁴⁺+B³⁺)/(La³⁺+Y³⁺+Gd³⁺+Yb³⁺) is greater than 1 but less than 2.5;

0-20% of Nb⁵⁺;

0-15% of Ti⁴⁺;

0-10% of Ta⁵⁺;

0-5% of W⁶⁺;

the total amount of Nb⁵⁺, Ti⁴⁺, Ta⁵⁺ and W⁶⁺ being 0-20%;

(Nb⁵⁺+Ti⁴⁺)/(Nb⁵⁺+Ti⁴⁺+Ta⁵⁺+W⁶⁺) being 0.7-1;

(Nb⁵⁺+Ti⁴⁺+Ta⁵⁺+W⁶⁺)/(Si⁴⁺+B³⁺) being 0.01-0.5;

(Nb⁵⁺+Ti⁴⁺+Ta⁵⁺+W⁶⁺)/(La³⁺+Y³⁺+Gd³⁺+Yb³⁺) being 0.02-0.6;

0-15% of Zr⁴⁺;

0-10% of Zn²⁺;

0-10% of Bi³⁺.

Furthermore, it also comprises:

the total amount of Li⁺, Na⁺ and K⁺ being less than 10%;

and/or the total amount of Ba²⁺, Mg²⁺, Ca²⁺ and Sr²⁺ being less than 10%.

Furthermore, it also comprises,

the total amount of Li⁺, Na⁺ and K⁺ being less than 5%;

and/or the total amount of Ba²⁺, Mg²⁺, Ca²⁺ and Sr²⁺ being less than 5%.

Furthermore, it comprises 2-15% of Si⁴⁺; and/or 25-45% of B³⁺ (exclusive of 45%); and/or 15-35% of La³⁺; and/or 0-13% of Y³⁺; and/or 0-10% of Gd³⁺; and/or 0-10% of Yb³⁺; and/or 0-15% of Nb⁵⁺; and/or 1-8% of Ti⁴⁺; and/or 0-7% of Ta⁵⁺; and/or 0-10% of Zr⁴⁺; and/or 0-5% of Zn²⁺; and/or 0-6% of Bi³⁺; and/or the total amount of Si⁴⁺ and B³⁺ is 30-60%; and/or the total amount of La³⁺, Y³⁺, Gd³⁺ and Yb³⁺ is 25-50%; and/or (Si⁴⁺+B³⁺)/(La³⁺+Y³⁺+Gd³⁺+Yb³⁺) is greater than 1 but less than 2.2; and/or the total amount of Nb⁵⁺, Ti⁴⁺, Ta⁵⁺ and W⁶⁺ is 0-15%; and/or (Nb⁵⁺+Ti⁴⁺)/(Nb⁵⁺+Ti⁴⁺+Ta⁵⁺+W⁶⁺) is 0.8-1; and/or (Nb⁵⁺+Ti⁴⁺+Ta⁵⁺+W⁶⁺)/(Si⁴⁺+B³⁺) is 0.02-0.4; and/or (Nb⁵⁺+Ti⁴⁺+Ta⁵⁺+W⁶⁺)/(La³⁺+Y³⁺+Gd³⁺+Yb³⁺) is 0.03-0.5.

Furthermore, it comprises 5-13% of Si⁴⁺; and/or 30-45% of B³⁺ (exclusive of 45%); and/or 20-35% of La³⁺; and/or 0-10% of Y³⁺; and/or 1-8% of Gd³⁺; and/or 0-5% of Yb³⁺; and/or 0.5-10% of Nb⁵⁺; and/or 3-8% of Ti⁴⁺; and/or 0-1.1% of Zn²⁺ (exclusive of 1.1%); and/or the total amount of Si⁴⁺ and B³⁺ is 40-55%; and/or the total amount of La³⁺, Y³⁺, Gd³⁺ and Yb³⁺ is 30-50%; and/or (Si⁴⁺+B³⁺)/(La³⁺+Y³⁺+Gd³⁺+Yb³⁺) is greater than 1 but less than 2; and/or the total amount of Nb⁵⁺, Ti⁴⁺, Ta⁵⁺ and W⁶⁺ is 3-15%; and/or (Nb⁵⁺+Ti⁴⁺)/(Nb⁵⁺+Ti⁴⁺+Ta⁵⁺+W⁶⁺) is 0.9-1; and/or (Nb⁵⁺+Ti⁴⁺+Ta⁵⁺+W⁶⁺)/(Si⁴⁺+B³⁺) is 0.03-0.35; and/or (Nb⁵⁺+Ti⁴⁺+Ta⁵⁺+W⁶⁺)/(La³⁺+Y³⁺+Gd³⁺+Yb³⁺) is 0.04-0.4.

Furthermore, it comprises 2.5-8% of Gd³⁺; and/or 3-7% of Ti⁴⁺.

Furthermore, the refractive index nd of the optical glass is 1.85-1.95, and the Abbe number vd is 32-40; when transmittance reaches 70%, the corresponding wave length is below 420 nm.

Furthermore, it comprises 2-15% of Si⁴⁺; and/or 45-60% of B³⁺; and/or 15-35% of La³⁺; and/or 0-13% of Y³⁺; and/or 0-10% of Gd³⁺; and/or 0-10% of Yb³⁺; and/or 0-15% of Nb⁵⁺; and/or 0-8% of Ti⁴⁺; and/or 0-7% of Ta⁵⁺; and/or 0-10% of Zr⁴⁺; and/or 0-5% of Zn²⁺; and/or 0-6% of Bi³⁺; and/or the total amount of Si⁴⁺ and B³⁺ is 40-65%; and/or the total amount of La³⁺, Y³⁺, Gd³⁺ and Yb³⁺ is 25-50%; and/or (Si⁴⁺+B³⁺)/(La³⁺+Y³⁺+Gd³⁺+Yb³⁺) is greater than or equal to 1.5 but less than 2.5; and/or the total amount of Nb⁵⁺, Ti⁴⁺, Ta⁵⁺ and W⁶⁺ is 0-15%; and/or (Nb⁵⁺+Ti⁴⁺)/(Nb⁵⁺+Ti⁴⁺+Ta⁵⁺+W⁶⁺) is 0.8-1; and/or (Nb⁵⁺+Ti⁴⁺+Ta⁵⁺+W⁶⁺)/(Si⁴⁺+B³⁺) is 0.02-0.4; and/or (Nb⁵⁺+Ti⁴⁺+Ta⁵⁺+W⁶⁺)/(La³⁺+Y³⁺+Gd³⁺+Yb³⁺) is 0.03-0.5.

Furthermore, it comprises 5-13% of Si⁴⁺; and/or 45-55% of B³⁺; and/or 20-35% of La³⁺; and/or 0-10% of Y³⁺; and/or 0-8% of Gd³⁺; and/or 0-5% of Yb³⁺; and/or 0.5-10% of Nb⁵⁺; and/or 0-5% of Ti⁴⁺; and/or 0.5-5% of Zn²⁺; and/or the total amount of Si⁴⁺ and B³⁺ is 50-65%; and/or the total amount of La³⁺, Y³⁺, Gd³⁺ and Yb³⁺ is 25-45%; and/or (Si⁴⁺+B³⁺)/(La³⁺+Y³⁺+Gd³⁺+Yb³⁺) is 1.7-2.3; and/or the total amount of Nb⁵⁺, Ti⁴⁺, Ta⁵⁺ and W⁶⁺ is 0-8%; and/or (Nb⁵⁺+Ti⁴⁺)/(Nb⁵⁺+Ti⁴⁺+Ta⁵⁺+W⁶⁺) is 0.9-1; and/or (Nb⁵⁺+Ti⁴⁺+Ta⁵⁺+W⁶⁺)/(Si⁴⁺+B³⁺) is 0.03-0.35; and/or (Nb⁵⁺+Ti⁴⁺+Ta⁵⁺+W⁶⁺)/(La³⁺+Y³⁺+Gd³⁺+Yb³⁺) is 0.04-0.4.

Furthermore, 1.1-3% of Zn²⁺; and/or 0-2.5% of Gd³⁺ (exclusive of 2.5%); and/or 0-3% of Ti⁴⁺ (exclusive of 3%).

Furthermore, the refractive index nd of the above glass is 1.78-1.85, and the Abbe number vd is 40-50; when transmittance reaches 80%, the corresponding wave length is below 420 nm.

Furthermore, it contains no Ta⁵⁺.

Furthermore, the refractive index nd of the glass is 1.78-1.95, the Abbe number νd is 32-50, the glass density is below 5 g/cm³, and the upper limit of glass devitrification temperature is below 1250° C.

Glass preform is formed of the above optical glass.

The optical element is formed of the above optical glass.

The advantages of the present invention are as follows: The present invention provides an optical glass with excellent transmittance, having refractive index nd of 1.78-1.95 and Abbe number vd of 32-50, and provides a glass preform and an optical element formed of the above optical glass. The optical element made by the above optical glass and the above glass preform or optical element blank, such as lens, can be used for optical systems.

DETAILED DESCRIPTION

To achieve the aim of the present invention, the inventor finds through repeated studies that, the optical glass with specific glass compositions can achieve the aim of the present invention.

Below will give description to the reasons of defining the composition range of the present invention, and the content of each ingredient and the total amount are represented by cation %, unless otherwise specially noted. The content and total amount is mole content.

Si⁴⁺ is a network formation cation of glass, with effects of maintaining the glass stability, keeping the viscosity suitable for forming molten glass, improving the chemical durability, etc. but if the content of Si⁴⁺ is lower than 1%, the above effects cannot be obtained; if the content is more than 20%, it is difficult to achieve the desired refractive index and Abbe number, and glass devitrification is aggravated due to refractory property. Therefore, the content of Si4⁺ is limited to 1-20%. Furthermore, the preferred lower limit of the content of Si⁴⁺ is 2%, more preferably 5%; the preferred upper limit is 15%, more preferably 13%, and further preferably 12%.

B³⁺ is a network formation cation of glass, as an indispensable ingredient of low dispersion glass, maintaining meltability, reducing liquidus temperature and improving glass stability. If the content is less than 25%, the glass stability is reduced, and the above effects cannot be obtained; if the content is more than 60%, it is difficult to meet the desired refractive index and the chemical durability will be worsened. Therefore, the content of B³⁺ in the present invention is 25-60%. Furthermore, the preferred lower limit of the content of B³⁺ is 30%, more preferably 32%; the preferred upper limit of the content of B³⁺ is 55%, more preferably 48%.

In particular, when the content of B³⁺ is 25-45%, furthermore, when the content of B³⁺ is 30-45% (exclusive of 45%), the chemical stability and heat resistance of the glass can be improved, and it is more conducive for the glass to obtain refractive index nd of 1.85-1.95 and Abbe number vd of 32-40; when the content of B³⁺ is 45-60%, furthermore, when the content of B³⁺ is 45-55%, it is more conducive for the glass to obtain refractive index nd of 1.78-1.85 and Abbe number vd of 40-50.

In addition, both B³⁺ and Si⁴⁺ are network forming components. The total content of B³⁺ and Si⁴⁺ shall be more than 30% from the perspectives of achieving the desired refractive index and maintaining the glass forming property; but it's difficult to obtain the required optical property if the total content of B³⁺ and Si⁴⁺ exceeds 70%. Therefore, the total content of B³⁺ and Si⁴⁺ is limited to 30-70%, preferably 40-65%.

In particular, when the total content of B³⁺ and Si⁴⁺ is 30-60%, furthermore, when the total content of B³⁺ and Si⁴⁺ is 40-55%, it is more conducive for the glass to obtain a refractive index nd of 1.85-1.95, an Abbe number vd of 32-40 and improve the chemical stability and heat resistance of the glass; when the total content of B³⁺ and Si⁴⁺ is 40-65%, furthermore, when the total content of B³⁺ and Si⁴⁺ is 50-65%, it is more conducive for the glass to obtain a refractive index nd of 1.78-1.85 and an Abbe number vd of 40-50.

La³⁺ is an essential component to achieve high refractive index and low dispersion. If the content is less than 10%, it is difficult to obtain the desired refractive index; if the content exceeds 40%, the upper limit of devitrification temperature will rise and the devitrification resistance will be poor. Therefore, the La³⁺ content is 10-40%. Furthermore, the preferred upper limit of the La³⁺ content is 35%, more preferably 30%; the preferred lower limit of the La³⁺ content is 15%, more preferably 20%.

The invention preferably introduces two or more rare earth oxides simultaneously. The inventor found that the coexistence of two or more rare earth cations will increase overall rare earth cations in the glass components, and by introducing these components with similar effects, the optical property with high refractive index and low dispersion can be realized and the glass devitrification can be better controlled.

The coexistence of Y³⁺ and La³⁺ has the effects of lowering the upper limit of devitrification temperature and greatly improving the devitrification resistance. At the same time, the glass transmittance is more excellent by introducing Y³⁺ than Gd³⁺ and Ta³⁺. However, if the Y³⁺ content exceeds 15%, the upper limit of devitrification temperature will rise and the devitrification resistance will be poor. Therefore, the Y³⁺ content is 0-15%. Furthermore, the preferred Y³⁺ content is 0-13%, more preferably 0-10%.

Gd³⁺ and Yb³⁺ can coexist with La³⁺ to have the effects of lowering the liquidus temperature, greatly improving the devitrification resistance and improving the chemical durability. The inventor found that the total content of La³⁺, Y³⁺, Gd³⁺ and Yb³⁺ is 20-55%, preferably 25-45%, from the perspectives of maintaining low dispersion, improving the refractive index and improving the devitrification resistance. The Gd³⁺ content is 0-10%, preferably 0-8%, and more preferably not involved. The Yb³⁺ content is 0-10%, preferably 0-5%, and more preferably not involved.

In particular, when the total content of La³⁺, Y³⁺, Gd³⁺ and Yb³⁺ is 25-50%, furthermore, when the total content of La³⁺, Y³⁺, Gd³⁺ and Yb³⁺is 30-50%, it is more conducive for the glass to obtain a refractive index nd of 1.85-1.95 and an Abbe number vd of 32-40, and the corresponding wavelength is below 420 nm when the transmittance reaches 70%.

In particular, when the Gd³⁺ content is 1-8%, furthermore, when the Gd³⁺ content is 2.5-8%, the liquidus temperature of the glass can be reduced and the moldability of the glass solution can be improved; when the Gd³⁺ content is 0-8%, furthermore, when the Gd³⁺ content is 0-2.5% (excluding 2.5%), the devitrification resistance of the glass can be more excellent.

In addition, if (Si⁴⁺+B³⁺)/(La³⁺+Y³⁺+Gd³⁺+Yb³⁺) is less than 1, the glass moldability will fall; but if it exceeds 2.5, it is difficult to maintain the required optical property, thus, (Si⁴⁺+B³⁺)/(La³⁺+Y³⁺+Gd³⁺+Yb³⁺) is greater than 1 but less than 2.5, preferably greater than 1 but less than 2.2, more preferably greater than 1 but less than 2.

In particular, when (Si⁴⁺+B³⁺)/(La³⁺+Y³⁺+Gd³⁺+Yb³⁺) is greater than 1 but less than 2.2, furthermore, when (Si⁴⁺+B³⁺)/(La³⁺+Y³⁺+Gd³⁺+Yb³⁺) is greater than 1 but less than 2, it is more conducive for the glass to obtain a refractive index nd of 1.85-1.95 and an Abbe number vd of 32-40, and the corresponding wavelength is below 420 nm when the glass transmittance reaches 70%; when (Si⁴⁺+B³⁺)/(La³⁺+Y³⁺+Gd³⁺+Yb³⁺) is greater than or equal to 1.5 but less than 2.5, furthermore, when (Si⁴⁺+B³⁺)/(La³⁺+Y³⁺+Gd³⁺+Yb³⁺) is 1.7-2.3, it is more conducive for the glass to obtain a refractive index nd of 1.78-1.85 and an Abbe number vd of 40-50, the corresponding wavelength is below 420 nm when the glass transmittance reaches 80%, and the devitrification property can be effectively improved.

In order to improve the refractive index of the glass while maintaining low dispersion, the invention introduces La³⁺ and other rare earth components as glass components. However, if the refractive index is increased only by rare earth components, the thermal stability of the glass will be remarkably lowered, and the components, such as Nb⁵⁺, Ti⁴⁺, Ta⁵⁺, W⁶⁺, Zr⁴⁺ and Bi⁴⁺, have the effects of improving the refractive index and dispersion, thus, at least one or more components of Nb⁵⁺, Ta⁵⁺, Ti⁴⁺, W⁶⁺, Zr⁴⁺ and Bi⁴⁺ are required.

Nb⁵⁺ has the effects of increasing the refractive index, lowering the upper limit of devitrification temperature of the glass and improving the devitrification resistance, and improving the thermal stability of the glass by coexisting with the glass component La³⁺ at the same time. If the Nb⁵⁺ content exceeds 20%, the upper limit of devitrification temperature of the glass will rise and the devitrification resistance will be poor, making it difficult to achieve the desired Abbe number and the glass pigmentation will be enhanced. Therefore, the Nb⁵⁺ content is 0-20%, preferably 0-15%, more preferably 0.5-10%.

Ti⁴⁺ also has the effects of increasing the refractive index, improving the chemical durability and devitrification resistance. If the Ti⁴⁺ content exceeds 15%, the glass transition temperature or the upper limit of devitrification temperature will rise, the compression moulding property will become poor and the trend of glass pigmentation will be shown. Therefore, the Ti⁴⁺ content is 0-15%, preferably 0-8%.

In particular, when the refractive index nd is greater than 1.85, the preferred Ti⁴⁺ content is 1-8%, more preferably 3-8%, further preferably 3-7%; and when the refractive index nd is less than 1.85, the preferred Ti⁴⁺ content is 0-8%, more preferably 0-5%, further preferably 0-3% (excluding 3%), much further preferably not involved.

Ta⁵⁺ has the effects of achieving high refractive index and low dispersion and improving the glass stability. However, Ta⁵⁺ is an expensive component, and if its content exceeds 10%, the upper limit of devitrification temperature will rise and the devitrification resistance will decrease. Therefore, the Ta⁵⁺ content is 0-10%, preferably 0-7% and more preferably not involved.

W⁶⁺ can increase the refractive index and lower the upper limit of devitrification temperature. However, if the W⁶⁺ content exceeds 5%, the compression moulding property will decrease and the trend of glass pigmentation will be shown. Therefore, the W⁶⁺ content is 0-5%.

In addition, in the components of Nb⁵⁺, Ti⁴⁺, Ta⁵⁺ and W⁶⁺ with which the glass refractive index can be improved, relatively speaking, Nb⁵⁺ is not easy to cause oxidation and reduction reaction of the mould-pressing forming mould, not easy to cause the defects including the sintering of the glass and the mould-pressing forming mould, the atomization and damage of the glass surface. In addition, if the total amount of Nb⁵⁺, Ti⁴⁺, Ta⁵⁺ and W⁶⁺ exceeds 20%, it is difficult to maintain the required optical properties and vitrification. Therefore, the total amount of Nb⁵⁺, Ti⁴⁺, Ta⁵⁺ and W⁶⁺ is 0-20%, preferably 0-15%, and preferably only introducing Nb⁵⁺.

Especially, when the total amount of Nb⁵⁺, Ti⁴⁺, Ta⁵⁺ and W⁶⁺ is 3-15%, the glass refractive index nd of 1.85-1.95 is more conducive to be obtained, with Abbe number vd of 32-40, and the moment the glass transmittance reaches 70%, the corresponding wave length is below 420 nm; when the total amount of Nb⁵⁺, Ti⁴⁺, Ta⁵⁺ and W⁶⁺ is 0-8%, the glass refractive index nd of 1.78-1.85 is more conductive to be obtained, with Abbe number vd of 40-50, and the moment the glass transmittance reaches 80%, the corresponding wave length is below 420 nm; meanwhile, the upper limit of devitrification temperature can be effectively decreased.

Controlling (Nb⁵⁺+Ti⁴⁺)/(Nb⁵⁺+Ti⁴⁺+Ta⁵⁺+W⁶⁺) to be 0.7-1 can realize the optical properties and the thermal stability of the glass, but cannot easily cause the redox reaction with the mould-pressing forming mould. More preferably, (Nb⁵⁺+Ti⁴⁺)/(Nb⁵⁺+Ti⁴⁺+Ta⁵⁺+W⁶⁺) is 0.8-1, further preferably (Nb⁵⁺+Ti⁴⁺)/(Nb⁵⁺+Ti⁴⁺+Ta⁵⁺+W⁶⁺) is 0.9-1.

In addition, in order to achieve the required optical properties while maintaining the glassiness, control (Nb⁵⁺+Ti⁴⁺+Ta⁵⁺+W⁶⁺)/(Si⁴⁺+B³⁺) to be 0.01-0.5, preferably 0.02-0.4, more preferably, 0.03-0.35; control (Nb⁵⁺+Ti⁴⁺+Ta⁵⁺+W⁶⁺)/(La³⁺+Y³⁺+Gd³⁺+Yb³⁺) to be 0.02-0.6, preferably 0.03-0.5, more preferably 0.04-0.4.

Zr⁴⁺ is also a component having an effect of increasing the refractive index. If the Zr⁴⁺ content exceeds 15%, the glass will be refractory, with glass moldability will be decreased and the upper limit of devitrification temperature is tended to rise. Therefore, the Zr⁴⁺ content is limited to 0-15%, preferably 0-10%.

Zn²⁺ has an effect of lowering the glass melting or transition temperature. But in the present invention, if the content is more than 10%, the refractive index will be decreased, with the chemical durability of the glass lowered, as a result, the content range of Zn²⁺ is 0-10%, preferably 0-5%, more preferably without Zn²⁺.

In particular, when the content of Zn²⁺ is 0-1.1% (exclusive of 1.1%), it is more conducive for the glass to obtain a refractive index nd of 1.85-1.95 and an Abbe number vd of 32-40; when the content of Zn²⁺ is 0.5-5%, furthermore, when the content of Zn²⁺ is 1.1-3%, it is more conducive for the glass to obtain a refractive index nd of 1.78-1.85 and an Abbe number vd of 40-50 and conductive to reduce the high temperature viscosity and the expansion coefficient of the glass. Bi³⁺ has the effect of improving refractive index and stability of the glass, but its dispersion is high. If the content is more than 10%, the Abbe number cannot be achieved, with the transmittance of light decreased in visible region. Therefore, the content range of Bi³⁺ is 0-10%, preferably 0-6% and more preferably without Bi³⁺.

Li⁺, Na⁺ and K⁺ are any components that improve glass meltability and decrease the glass transition temperature. If the total content of Li⁺, Na⁺ and K⁺ exceeds 10%, it is difficult to achieve a desired refractive index and the glass stability and chemical durability are also decreased. Therefore, the total amount of Li⁺, Na⁺ and K⁺ is less than 10%, preferably less than 5%, more preferably not contained.

Ba²⁺, Mg²⁺, Ca²⁺ and Sr²⁺ have effects of improving the glass meltability and decreasing glass transition temperature. However, if the total amount of Ba²⁺, Mg²⁺, Ca²⁺ and Sr²⁺ is more than 10%, then the glass devitrification resistance deteriorates, with the refractive index decreased and the chemical durability deteriorated. Therefore, the total amount of Ba²⁺, Mg²⁺, Ca²⁺ and Sr²⁺ is less than 10%, preferably less than 5%, more preferably not contained.

The optical glass of the present invention is the oxide glass, and the anionic component is actually composed of O²⁻. As described above, a small amount of Cl⁻ and F⁻ can be added as a clarifying agent, but the content of O2⁻ is preferably greater than or equal to 98 anions %, more preferably greater than or equal to 99 anions %, further preferably greater than or equal to 99.5 anions %, most preferably 100 anions %.

The refractive index nd range of the optical glass of the present invention is 1.78-1.95. When the high refractive index is preferred, preferably the lower limit of the refractive index nd is 1.80; and proceeding from the glass stability, preferably the upper limit of the refractive index is 1.92.

The Abbe number vd of the optical glass of the present invention is 32-50. When chromatic aberration is corrected in combination with lens made of highly dispersible glass, large Abbe number vd is favorable. From this point of view, the lower limit of the Abbe number vd is preferably 35, and on the other hand, alleviating the upper limit of Abbe number vd plays a favorable role in maintaining and improving the stability of the glass. From this point of view, the upper limit of the Abbe number vd is preferably 48.

Light transmissivity of the optical glass of the present invention will be described in the following paragraphs.

In the optical glass of the present invention, when the glass nd is greater than or equal to 1.85, the corresponding wavelength (λ₇₀) is less than or equal to 420 nm when its glass transmittance reaches 70%; when the glass nd is less than 1.85, the corresponding wavelength (λ₈₀) is less than or equal to 420 nm when its glass transmittance reaches 80%.

In the present invention, λ₇₀ is preferably less than or equal to 410 nm, then preferably less than or equal to 400 nm, and more preferably less than or equal to 390 nm.

In the present invention, λ₈₀ is preferably less than or equal to 410 nm, then preferably less than or equal to 400 nm, and more preferably less than or equal to 390 nm.

The above λ₇₀ or λ₈₀ is the wavelength with the light transmittance of 70% or 80% in the wavelength range of 280-700 nm. Here, the light transmittance is the spectral transmission obtained by using a glass sample with the planes which are grinded into the thickness of 10.0±0.1 mm & paralleled to one another and from the incident light which comes from the vertical direction of the grinded planes. The spectral transmittance also includes the reflection loss of the light on the sample surface. Besides, the above grinding means that the surface roughness, relative to a wavelength of a determined wavelength domain, is smoothed to be in a small enough state.

The upper limit of devitrification temperature of the optical glass provided by the present invention is preferably less than or equal to 1250° C., more preferably less than or equal to 1200° C., further preferably less than or equal to 1150° C., and most preferably less than or equal to 1100° C.

The density ρ of the optical glass provided by the present invention is preferably less than or equal to 5 g/cm³, more preferably less than or equal to 4.95 g/cm³, further preferably less than or equal to 4.8 g/cm³, furthermore preferably less than or equal to 4.5 g/cm³, and most preferably less than or equal to 4.3 g/cm³.

A manufacturing method of the optical glass provided by the present invention will be described in the following paragraphs.

Corresponding to target glass composition, powdery compound materials or broken glass materials are weighed and mixed, and then heated and molten after being supplied to a platinum alloy melting container. After the above raw materials are molten completely and vitrified, temperature of the molten glass rises and the molten glass is clarified. The clarified molten glass is unified by virtue of mixing of a mixer, and then continuously supplied to a glass outflow pipe to outflow for quenching and solidification, so as to obtain a glass shaped object.

Besides, from the perspective of uniformly low-colored glass with stable features such as optical feature, the molten temperature of the optical glass is preferably within the scope of 1300-1450° C.

A glass preform and an optical element provided by the present invention are made of the optical glass provided by the present invention. The glass preform and the optical element provided by the present invention have such features as high refractive index and low dispersion, are free of Ge and other expensive ingredients. As a result of this, the optical elements such as various lenses and prisms with high optical value can be provided with low cost.

Embodiments

The technical scheme of the present invention will be further illustrated by the following embodiments, but the present invention is not limited by these embodiments. By referring to the following embodiments and applying a method of regulating contents of the above various glass ingredients, the optical glass provided by the present invention can be obtained.

Firstly, nitrate, carbonate, sulfate, hydroxide, oxide, boric acid and so on are applied to obtain an oxide glass of a composition (represented by cation %) shown in Tables 1-9; various raw material powder is weighed for fully mixing to obtain a mixed raw material; the mixed raw material is placed into a platinum made crucible to be heated, molten, clarified and mixed at 1300-1450° C., so as to obtain a uniform molten glass. The molten glass is flowed into a preheated casting mould for quenching, and then slowly cooled after being kept for 2 h at the temperature nearby a glass transition temperature, so as to obtain various optical glasses in embodiments 1-16.

Besides, all anion ingredients of embodiments 1-72 are O²⁻. The features of glasses are determined by the methods shown as follows:

(1) Refractive Index (nd) and Abbe Number (vd)

The refractive index and Abbe number are tested as per GB/T 7962.1-1987 Colorless Optical Glass Test Methods: Refractive Index and Coefficient of Dispersion.

(2) Pigmentation Degree of Glass (λ₇₀ and λ₈₀)

Pigmentation degree is applied to represent the characteristic of short wave transmission spectrum of the optical glass. The glass is made into a sample with thickness of 10 mm±0.1 mm. When the glass nd is greater than or equal to 1.85, the corresponding wavelength (λ₇₀) is tested when the glass transmittance reaches 70%; when the glass nd is less than 1.85, the corresponding wavelength (λ₈₀) is tested when the glass transmittance reaches 80%.

(3) Glass Density (ρ)

The density (φ is tested as per GB/T 7962.20-1987 Colorless Optical Glass Test Methods—Density.

(4) Upper Limit of Devitrification Temperature

The devitrification property of the glass is tested by a temperature gradient furnace method which comprises the following steps: processing the glass into samples (180 mm×10 mm×10 mm), polishing lateral sides, placing the samples into a furnace having a temperature gradient, taking out the samples after the temperature is kept for 4 hours, and observing the devitrification of glass under a microscope, wherein the maximum temperature corresponding to the appearance of crystals is the upper limit of devitrification temperature of the glass.

TABLE 1 Embodiments 1-8 Cation 1 2 3 4 5 6 7 8 B³⁺ 30.1 48.9 55.6 32.9 35.7 45.9 47.2 53.5 Si⁴⁺ 14.4 7.8 6.4 12.8 10.3 8.3 5.8 7.6 B³⁺ + Si⁴⁺ 44.5 56.7 62 45.7 46 54.2 53 61.1 La³⁺ 30.7 22.9 18.8 34.7 25.5 24.8 30.6 22.5 Y³⁺ 4.7 8.6 7.1 3.4 8.5 7.8 4.4 8.6 Gd³⁺ 6 0 0 0 4.8 0 0 0 Yb³⁺ 0 0 0 0 0 0 0 0 ΣLn³⁺ 41.4 31.5 25.9 38.1 38.8 32.6 35 31.1 (B³⁺ + Si⁴⁺)/ΣLn³⁺ 1.07 1.8 2.39 1.19 1.19 1.66 1.51 1.96 Nb⁵⁺ 3.8 4.9 4.7 9.1 6.5 3.3 5.5 1.9 Ti⁴⁺ 5.7 0 0 7.0 4.3 0 3.1 0 Ta⁵⁺ 0 0 0 0 0 0 0 0 W⁶⁺ 0 0 2.0 0 0 0 0 0 ΣHR 9.5 4.9 6.7 16.1 10.8 3.3 8.6 1.9 (Nb⁵⁺ + Ti⁴⁺)/ΣHR 1 1 0.7 1 1 1 1 1 ΣHR/(B³⁺ + Si⁴⁺) 0.21 0.08 0.1 0.35 0.23 0.06 0.16 0.03 ΣHR/ΣLn³⁺ 0.23 0.16 0.25 0.42 0.27 0.1 0.24 0.06 Zr⁴⁺ 4.6 5.2 2.9 0.1 4.4 6.9 3.4 4.8 Zn²⁺ 0 1.7 2.5 0 0 3 0 1.1 Bi³⁺ 0 0 0 0 0 0 0 0 ΣR⁺ 0 0 0 0 0 0 0 0 ΣR²⁺ 0 0 0 0 0 0 0 0 Total 100 100 100 100 100 100 100 100 nd 1.910 1.835 1.810 1.904 1.901 1.830 1.831 1.804 vd 35.7 42.7 45.9 37. 8 37.1 43.1 43.2 46.6 (g/cm³) 5.0 4.57 4.45 4.9 4.95 4.59 4.63 4.49 λ₇₀ (nm) 400 395 390 λ₈₀ (nm) 400 395 405 410 390 Upper limit of 1250 1190 1140 1200 1230 1180 1150 1140 devitrification temperature (° C.)

TABLE 2 Embodiments 9-16 Cation 9 10 11 12 13 14 15 16 B³⁺ 40.2 52.1 51.6 34.6 36.3 46.8 40.2 54.5 Si⁴⁺ 8.3 4.6 8.4 7.9 9.3 5.3 4.7 6.6 B³⁺ + Si⁴⁺ 48.5 56.7 60 42.5 45.6 52.1 44.9 61.1 La³⁺ 27.4 18.8 23.8 35.3 28.5 30.1 39.8 25.1 Y³⁺ 9.1 10.6 7.5 3.4 8.1 3.9 4.4 4.6 Gd³⁺ 2.5 0 0 0 1.9 0 0 0 Yb³⁺ 0 0 0 0 0 2 0 0 ΣLn³⁺ 39 29.4 31.3 38.7 38.5 36 44.2 29.7 (B³⁺ + Si⁴⁺)/ΣLn³⁺ 1.24 1.92 1.91 1.09 1.18 1.44 1.01 2.05 Nb⁵⁺ 4.8 6.9 3.1 9.7 7.4 3.4 5 2.8 Ti⁴⁺ 1.2 0 0 3.0 5.3 0 4 0 Ta⁵⁺ 0 0 0 0 0 0.5 0 0 W⁶⁺ 0 0 0 0 0 0.2 0 0 ΣHR 6 6.9 3.1 12.7 12.7 4.1 9 2.8 (Nb⁵⁺ + Ti⁴⁺)/ΣHR 1 1 1 1 1 0.82 1 1 ΣHR/(B³⁺ + Si⁴⁺) 0.12 0.12 0.05 0.29 0.27 0.07 0.2 0.04 ΣHR/ΣLn³⁺ 0.15 0.23 0.1 0.32 0.32 0.11 0.2 0.09 Zr⁴⁺ 5.1 6.3 4.4 5.1 3.2 7.1 1.9 2.7 Zn²⁺ 0 0.7 1.2 0 0 0.7 0 2.7 Bi³⁺ 0 0 0 1 0 0 0 0 ΣR⁺ 0 0 0 0 0 1 0 0 ΣR²⁺ 1.4 0 0 0 0 0 0 1 Total 100 100 100 100 100 100 100 100 nd 1.910 1.831 1.807 1.902 1.902 1.805 9110 1'807 vd 35.4 42.5 45.9 37.1 37.0 46.1 35.4 46.5 ρ 4.9 4.61 4.47 4.85 4.95 4.50 5.0 4.48 λ₇₀ (nm) 400 395 390 390 λ₈₀ (nm) 390 400 395 390 Upper limit of 1220 1190 1180 1250 1200 1150 1200 1160 devitrification temperature (° C.)

TABLE 3 Embodiments 17-24 Cation 17 18 19 20 21 22 23 24 B³⁺ 34.6 37.2 31.7 34.5 28.7 38.5 40.7 33.7 Si⁴⁺ 11.5 7.1 15.4 9.4 17.6 12.5 17.2 8.4 La³⁺ 26.4 23.7 20.6 25.6 22.1 19.4 15.9 30 Y³⁺ 8.2 6.4 2.8 7.2 8.5 5.2 12.4 3.8 Gd³⁺ 3.6 5.2 7.2 4.3 4.7 6.1 1.5 2.3 Yb³⁺ 1.7 0 0 0 0.1 2.4 0 0 Nb⁵⁺ 4.6 3.7 2.5 5.8 8.2 6.6 9.4 10.5 Ti⁴⁺ 3.7 5.7 10.2 6.7 5.4 7.3 2.2 4.9 Ta⁵⁺ 0 0 1.4 0 0 0.2 0 0 W⁶⁺ 2.3 3.8 0 0 0 0.3 0 0 Zr⁴⁺ 2.7 4.6 8.2 5.3 3.2 1.5 0 6.4 Zn²⁺ 0 0 0 1.2 0 0 0.7 0 Bi³⁺ 0 1.4 0 0 0.7 0 0 0 ΣR⁺ 0.7 0 0 0 0.5 0 0 0 ΣR²⁺ 0 1.2 0 0 0.3 0 0 0 Total 100 100 100 100 100 100 100 100 nd 1.911 1.906 1.892 1.914 1.908 1.872 1.869 1.924 vd 35.2 37.4 33.5 36.4 33.4 38.1 38.5 37.2 (g/cm³) 4.82 4.95 5.0 4.92 4.85 4.93 4.84 4.91 λ₇₀ (nm) 405 408 410 400 396 401 392 395 λ₈₀ (nm) Upper limit of 1220 1230 1225 1230 1235 1240 1225 1230 devitrification temperature (° C.) B³⁺ + Si⁴⁺ 46.1 44.3 47.1 43.9 46.3 51 57.9 42.1 ZLn³⁺ 39.9 35.3 30.6 37.1 35.4 33.1 29.8 36.1 (B³⁺ + Si⁴⁺)/ΣLn³⁺ 1.155 1.255 1.539 1.183 1.308 1.541 1.943 1.166 ΣHR 10.6 13.2 14.1 12.5 13.6 14.4 11.6 15.4 (Nb⁵⁺ + Ti⁴⁺)/ΣHR 0.783 0.712 0.901 1 1 0.965 1 1 ΣHR/(B³⁺ + Si⁴⁺) 0.23 0.298 0.299 0.285 0.294 0.282 0.200 0.366 ΣHR/ΣLn³⁺ 0.266 0.374 0.461 0.337 0.384 0.435 0.389 0.427

TABLE 4 Embodiment 25-32 Cation 25 26 27 28 29 30 31 32 B³⁺ 27.4 33.1 35.8 30.1 32.3 40.2 36.2 28.6 Si⁴⁺ 16.2 10.3 11.4 10.2 15.8 8 7.3 11.5 La³⁺ 15.4 17.1 24.5 13.4 22.1 27.1 18.8 24.5 Y³⁺ 13.2 4.3 8.6 11.5 6.1 0 9.2 7.1 Gd³⁺ 3.7 8.2 5.3 7.4 4.5 2.6 6.5 4 Yb³⁺ 1.1 0 0 0 0.4 0 0.5 0 Nb⁵⁺ 15.2 12.4 5.7 0.7 6.9 10.2 0 5.8 Ti⁴⁺ 0 1.7 5.1 13.1 5.7 6.7 13.3 6.4 Ta⁵⁺ 0.5 0 0 0 0 0 0 0 W⁶⁺ 0 0 0 0.6 0 0 0 0 Zr⁴⁺ 7.3 9.1 3.6 10.5 6.2 5.2 8.2 12.1 Zn²⁺ 0 0 0 0 0 0 0 0 Bi³⁺ 0 1.3 0 0.4 0 0 0 0 ΣR⁺ 0 0 0 2.1 0 0 0 0 ΣR²⁺ 0 2.5 0 0 0 0 0 0 Total 100 100 100 100 100 100 100 100 nd 1.876 1.895 1.910 1.875 1.904 1.911 1.892 1.912 vd 33.5 35.6 37.1 36.2 35.8 38.2 37.6 33.4 (g/cm³) 4.89 4.90 4.93 4.80 4.89 5.00 4.92 4.93 λ₇₀ (nm) 390 392 398 410 395 394 412 398 λ₈₀ (nm) Upper limit of 1210 1220 1215 1230 1200 1215 1205 1215 devitrification temperature (° C.) B³⁺ + Si⁴⁺ 43.6 43.4 47.2 40.3 48.1 48.2 43.5 40.1 ΣLn³⁺ 33.4 29.6 38.4 32.3 33.1 29.7 35 35.6 (B³⁺ + Si⁴⁺)/ΣLn³⁺ 1.305 1.466 1.229 1.248 1.453 1.623 1.243 1.126 ΣHR 15.7 14.1 10.8 14.4 12.6 16.9 13.3 12.2 (Nb⁵⁺ + Ti⁴⁺)/ΣHR 0.968 1 1 0.958 1 1 1 1 ΣHR/(B³⁺ + Si⁴⁺) 0.360 0.325 0.229 0.357 0.262 0.351 0.306 0.304 ΣHR/ΣLn³⁺ 0.470 0.476 0.281 0.446 0.381 0.569 0.38 0.343

TABLE 5 Embodiment 33-40 Cation 33 34 35 36 37 38 39 40 B³⁺ 34.7 35.9 41.6 34.6 42.8 38.8 35.7 35.7 Si⁴⁺ 11.2 5.7 9 10.8 8.4 18.2 12.4 11.7 La³⁺ 23.6 27.3 21.1 26.2 33.4 18.3 20.6 23.6 Y³⁺ 7.8 2.5 5.1 9.1 3.5 14.2 11.5 7.4 Gd³⁺ 5.5 5.1 7.3 3.8 4.3 3.3 6.2 5.7 Yb³⁺ 0.3 3.4 0 0 0 0 0 0.5 Nb⁵⁺ 7.9 5.4 6.6 5.9 2.4 2.6 0.8 6.7 Ti⁴⁺ 3.8 2.6 6.7 5.1 1.6 3.2 1.6 4.2 Ta⁵⁺ 0 0 0 0 0 0 0 0 W⁶⁺ 0 2.1 0 0 0 0 0 0 Zr⁴⁺ 5.2 7.2 2.6 4.2 3.6 1.4 11.2 4.5 Zn²⁺ 0 0.6 0 0 0 0 0 0 Bi³⁺ 0 0 0 0.3 0 0 0 0 ΣR⁺ 0 0.7 0 0 0 0 0 0 ΣR²⁺ 0 1.5 0 0 0 0 0 0 Total 100 100 100 100 100 100 100 100 nd 1.912 1.908 1.901 1.913 1.932 1.872 1.900 1.901 vd 37.0 36.8 38.4 36.8 38.5 37.4 37.1 37.1 (g/cm³) 4.92 4.89 4.91 4.93 4.92 4.92 5.00 4.89 λ₇₀ (nm) 390 395 397 396 391 394 391 393 λ₈₀ (nm) Upper limit of 1220 1215 1230 1220 1230 1210 1205 1210 devitrification temperature (° C.) B³⁺ + Si⁴⁺ 45.9 41.6 50.6 45.4 51.2 57 48.1 47.4 ΣLn³⁺ 37.2 38.3 33.5 39.1 41.2 35.8 38.3 37.2 (B³⁺ + Si⁴⁺)/ΣLn³⁺ 1.234 1.087 1.510 1.161 1.243 1.592 1.256 1.274 ΣHR 11.7 10.1 13.3 11 4 5.8 2.4 10.9 (Nb⁵⁺ + Ti⁴⁺)/ΣHR 1 0.792 1 1 1 1 1 1 ΣHR/(B³⁺ + Si⁴⁺) 0.255 0.243 0.263 0.242 0.0781 0.102 0.05 0.23 ΣHR/ΣLn³⁺ 0.315 0.264 0.397 0.281 0.097 0.162 0.063 0.293

TABLE 6 Embodiments 41-48 Cation 41 42 43 44 45 46 47 48 B³⁺ 43.1 38.5 34.5 37.7 35.7 50.4 45.5 46.1 Si⁴⁺ 17.6 18.3 11.2 5.2 11.1 7.1 2.6 11.2 La³⁺ 14.7 24.3 24.9 14.3 25.5 22.4 18.2 18.4 Y³⁺ 3.2 4.1 7.5 13.2 8 8.4 7.1 4.5 Gd³⁺ 6.6 4.9 6.3 7.5 4.6 0 0 2.3 Yb³⁺ 3.2 0 0 0 0 0 0 2.1 Nb⁵⁺ 2.7 1.5 6.2 7.8 5.8 5.2 12.4 4.5 Ti⁴⁺ 1.4 2.1 4.7 6 3.2 0 0 0.4 Ta⁵⁺ 0 0 0 0 0 0 0.6 0 W⁶⁺ 0 0 0.5 0 0 0 1.5 0 Zr⁴⁺ 1.2 2.6 4.2 8.3 6.1 4.9 9.1 3.2 Zn²⁺ 0 0 0 0 0 1.6 2.7 4.4 Bi³⁺ 2.2 0 0 0 0 0 0 0 ΣR⁺ 0 3.7 0 0 0 0 0 0.8 ΣR²⁺ 4.1 0 0 0 0 0 0.3 2.1 Total 100 100 100 100 100 100 100 100 nd 1.881 1.902 1.910 1.875 1.905 1.834 1.815 1.820 vd 38.8 37.5 36.7 37.2 37.1 42.6 43.8 43.3 (g/cm³) 4.95 4.91 4.93 4.92 4.90 4.52 4.45 4.51 λ₇₀ (nm) 392 393 395 397 393 λ₈₀ (nm) 395 394 390 Upper limit of 1205 1210 1220 1215 1210 1135 1140 1155 devitrification temperature (° C.) B³⁺ + Si⁴⁺ 60.7 56.8 45.7 42.9 46.8 57.5 48.1 57.3 ΣLn³⁺ 27.7 33.3 38.7 35 38.1 30.8 25.3 27.3 (B³⁺ + Si⁴⁺)/ΣLn³⁺ 2.191 1.706 1.181 1.226 1.228 1.867 1.901 2.099 ΣHR 4.1 3.6 11.4 13.8 9 5.2 14.5 4.9 (Nb⁵⁺ + Ti⁴⁺)/ΣHR 1 1 0.956 1 1 1 0.855 1 ΣHR/(B³⁺ + Si⁴⁺) 0.068 0.063 0.25 0.322 0.192 0.090 0.302 0.086 ΣHR/ΣLn³⁺ 0.148 0.108 0.295 0.394 0.236 0.169 0.573 0.18

TABLE 7 Embodiments 49-56 Cation 49 50 51 52 53 54 55 56 B³⁺ 52.1 56.4 48.1 46.2 57.1 45.6 47.2 49.6 Si⁴⁺ 3.4 2 6.4 10.2 4.2 12.2 5.2 7.2 La³⁺ 16.3 20.1 18.3 17.2 22.6 15.9 30 19.2 Y³⁺ 12.5 4.3 6.5 9.4 7.3 8.4 0 11.4 Gd³⁺ 0 1.5 0 0 0 2 0 0 Yb³⁺ 1.2 0 0 0 0 3.3 4.7 0 Nb⁵⁺ 8.2 6.7 10.5 2.5 3.5 0 4.4 5.7 Ti⁴⁺ 0 1.1 0 0 0 2.1 0 0 Ta⁵⁺ 0 0.6 0 0 0 0.6 0 0 W⁶⁺ 0 2.5 0 0 0 0 0 0 Zr⁴⁺ 1.5 2.6 8.2 10.4 4.1 6.3 7.2 5.4 Zn²⁺ 3.3 1.4 2 4.1 1.2 1.6 1.3 1.5 Bi³⁺ 1.5 0 0 0 0 0 0 0 ΣR⁺ 0 0.8 0 0 0 0.6 0 0 ΣR²⁺ 0 0 0 0 0 1.4 0 0 Total 100 100 100 100 100 100 100 100 nd 1.804 1.793 1.832 1.830 1.791 1.817 1.841 1.832 vd 48.5 47.6 41.6 42.5 46.3 46.5 41.9 42.3 (g/cm³) 4.66 4.35 4.48 4.51 4.62 4.50 4.47 4.60 λ₇₀ (nm) λ₈₀ (nm) 389 412 391 393 390 398 390 390 Upper limit of 1120 1130 1125 1110 1150 1160 1145 1105 devitrification temperature (° C.) B³⁺ + Si⁴⁺ 55.5 58.4 54.5 56.4 61.3 57.8 52.4 56.8 ΣLn³⁺ 30 25.9 24.8 26.6 29.9 29.6 34.7 30.6 (B³⁺ + Si⁴⁺)/ΣLn³⁺ 1.85 2.2548 2.1976 2.1203 2.0502 1.9527 1.5101 1.8562 ΣHR 8.2 10.9 10.5 2.5 3.5 2.7 4.4 5.7 (Nb⁵⁺ + Ti⁴⁺)/ΣHR 1 0.716 1 1 1 0.778 1 1 ΣHR/(B³⁺ + Si⁴⁺) 0.148 0.187 0.193 0.044 0.057 0.047 0.084 0.100 ΣHR/ΣLn³⁺ 0.273 0.421 0.423 0.094 0.117 0.091 0.127 0.186

TABLE 8 Embodiments 57-64 Cation 57 58 59 60 61 62 63 64 B³⁺ 49.6 50.5 54.8 45.3 47.1 41.2 51.5 55.3 Si⁴⁺ 2.8 6.2 6.2 5.5 9.3 7.3 7.8 5.1 La³⁺ 26.7 21.3 16.6 18.2 24.1 22.4 23.4 15.6 Y³⁺ 13.5 6.3 10.5 7.6 8.3 7.6 9.3 11.4 Gd³⁺ 0 0 0 0 0 1.5 0 0 Yb³⁺ 0 1.1 0 0 0 0 0 0 Nb⁵⁺ 1.8 5.2 7.1 8.3 4.2 6.8 2.7 3.5 Ti⁴⁺ 0 1.2 0 1.4 0 0 0 0 Ta⁵⁺ 0 0 0 2.5 0 0 0 0 W⁶⁺ 0 0.4 0 0 0 0 0 0 Zr⁴⁺ 1.5 6.3 3.5 8.5 5.3 9.4 4.5 7.6 Zn²⁺ 4.1 1.5 1.3 2.7 1.7 2.2 0.8 1.5 Bi³⁺ 0 0 0 0 0 0 0 0 ΣR⁺ 0 0 0 0 0 1.6 0 0 ΣR²⁺ 0 0 0 0 0 0 0 0 Total 100 100 100 100 100 100 100 100 nd 1.833 1.832 1.806 1.835 1.840 1.820 1.836 1.801 vd 42.6 43.5 47.1 42.5 41.6 42.5 43.0 48.2 (g/cm³) 4.54 4.62 4.55 4.58 4.50 4.28 4.58 4.47 λ₇₀ (nm) λ₈₀ (nm) 394 403 398 401 396 394 395 390 Upper limit of 1130 1135 1120 1140 1135 1120 1125 1115 devitrification temperature (° C.) B³⁺ + Si⁴⁺ 52.4 56.7 61 50.8 56.4 48.5 59.3 60.4 ΣLn³⁺ 40.2 28.7 27.1 25.8 32.4 31.5 32.7 27 (B³⁺ + Si⁴⁺)/ΣLn³⁺ 1.304 1.976 2.251 1.969 1.741 1.54 1.814 2.237 ΣHR 1.8 6.8 7.1 12.2 4.2 6.8 2.7 3.5 (Nb⁵⁺ + Ti⁴⁺)/ΣHR 1 0.941 1 0.795 1 1 1 1 ΣHR/(B³⁺ + Si⁴⁺) 0.034 0.12 0.116 0.240 0.075 0.140 0.046 0.058 ΣHR/ΣLn³⁺ 0.045 0.237 0.262 0.473 0.13 0.216 0.083 0.13

TABLE 9 Embodiment 65-72 Cation 65 66 67 68 69 70 71 72 B³⁺ 45 48.9 47.2 52.3 53.5 47.5 55.2 42.9 Si⁴⁺ 5.2 3.2 2 7.2 6.8 8.2 4.5 14.2 La³⁺ 20.7 24.5 27.4 21.4 22.1 23.4 19.5 18.8 Y³⁺ 10.8 11.1 5.8 8.1 6.8 9.7 7.4 8 Gd³⁺ 1.4 0 0 0 0 0 0 0 Yb³⁺ 0 0 0 0 1.8 0 0 1.2 Nb⁵⁺ 6.3 4.7 9.2 4.8 7.2 5.7 6.5 3.8 Ti⁴⁺ 1.2 0 0 0 0 0 0 0.7 Ta⁵⁺ 0 0 1.3 0 0 0 0 0 W⁶⁺ 0.6 0 0 0 0 0 0 0.3 Zr⁴⁺ 3.7 6.2 4.9 4.2 0 5.5 5.3 8.2 Zn²⁺ 1.6 1.4 2.2 2 1.3 0 1.6 1.9 Bi³⁺ 0 0 0 0 0.5 0 0 0 ΣR⁺ 2.2 0 0 0 0 0 0 0 ΣR²⁺ 1.3 0 0 0 0 0 0 0 Total 100 100 100 100 100 100 100 100 nd 1.835 1.840 1.822 1.816 1.825 1.837 1.792 1.820 vd 41.6 42.5 43.5 47.2 42.2 43.1 47.5 45.8 (g/cm³) 4.29 4.38 4.41 4.51 4.56 4.60 4.55 4.47 λ₇₀ (nm) λ₈₀ (nm) 400 398 396 395 397 396 398 399 Upper limit of 1120 1130 1120 1150 1110 1135 1130 1120 devitrification temperature (° C.) B³⁺ + Si⁴⁺ 50.2 52.1 49.2 59.5 60.3 55.7 59.7 57.1 ΣLn³⁺ 32.9 35.6 33.2 29.5 30.7 33.1 26.9 28 (B³⁺ + Si⁴⁺)/ΣLn³⁺ 1.526 1.464 1.482 2.017 1.964 1.683 2.219 2.039 ΣHR 8.1 4.7 10.5 4.8 7.2 5.7 6.5 4.8 (Nb⁵⁺ + Ti⁴⁺)/ΣHR 0.926 1 0.876 1 1 1 1 0.938 ΣHR/(B³⁺ + Si⁴⁺) 0.161 0.090 0.213 0.081 0.119 0.102 0.109 0.084 ΣHR/ΣLn³⁺ 0.246 0.132 0.316 0.163 0.235 0.172 0.242 0.171

In the above tables 1-9:

ΣLn³⁺ refers to the total amount of La³⁺, Y³⁺, Gd³⁺ and Yb³⁺;

ΣHR refers to the total amount of Nb⁵⁺, Ti⁴⁺, Ta⁵⁺ and W⁺;

ΣR⁺ refers to the total amount of Li⁺, Na⁺ and K⁺;

ΣR²⁺ refers to the total amount of Mg²⁺, Ca²⁺, Sr²⁺ and Ba²⁺.

The present invention relates to the optical glass, with high refractive index and low dispersion, which can be supplied stably, applicable to the glass preform and an optical element for shaping. 

The invention claimed is:
 1. An optical glass, represented by cation %, comprising: 30-less than 45% of B³⁺; the total amount of Si⁴⁺ and B³⁺ being 40-55%; 5-13% of Si⁴⁺; 20-35% of La³⁺; 0-15% of Y³⁺; 1-8% of Gd³⁺; 0-5% of Yb³⁺; the total amount of La³⁺, Y³⁺, Gd³⁺ and Yb³⁺ being 30-50%; (Si⁴⁺+B³⁺)/(La³⁺+Y³⁺+Gd³⁺+Yb³⁺) is greater than 1 but less than 1.8; 0.5-10% of Nb⁵⁺; 3-8% of Ti⁴⁺; 0-10% of Ta⁵⁺; 0-5% of W⁶⁺; the total amount of Nb⁵⁺, Ti⁴⁺, Ta⁵⁺ and W⁶⁺ being 3.5-15%; (Nb⁵⁺+Ti⁴⁺)/(Nb⁵⁺+Ti⁴⁺+Ta⁵⁺+W⁶⁺) being 0.7-1; (Nb⁵⁺+Ti⁴⁺+Ta⁵⁺+W⁶⁺)/(Si⁴⁺+B³⁺) being 0.06-0.35; (Nb⁵⁺+Ti⁴⁺+Ta⁵⁺+W⁶⁺)/(La³⁺+Y³⁺+Gd³⁺+Yb³⁺) being 0.07-0.4; 0-10% of Zr⁴⁺; 0-10% of Zn²⁺; 0-10% of Bi³⁺.
 2. The optical glass according to claim 1, also optionally comprising: Li⁺, Na⁺ and K⁺ in a total amount of less than 10%; and Ba²⁺, Mg²⁺, Ca²⁺ and Sr²⁺ in a total amount of less than 10%.
 3. The optical glass according to claim 2, wherein: the total amount of Li⁺, Na⁺ and K⁺ being less than 5%; and the total amount of Ba²⁺, Mg²⁺, Ca²⁺ and Sr²⁺ being less than 5%.
 4. The optical glass according to claim 1, wherein 2.5-8% of Gd³⁺; and 3-7% of Ti⁴⁺.
 5. The optical glass according to claim 1, wherein the composition is free of Ta⁵⁺.
 6. The optical glass according to claim 1, wherein the refractive index nd of glass is 1.85-1.95, the Abbe number νd is 32-40, and the corresponding wavelength is below 420 nm when the transmittance of glass reaches 70%, the glass density is below 5 g/cm³, and the upper limit of devitrification temperature of glass is below 1250° C.
 7. A glass preform, which is made of the optical glass according to claim
 1. 8. An optical element, which is made of the optical glass according to claim
 1. 9. An optical glass, represented by cation %, comprising: 5-13% of Si⁴⁺; 45-55% of B³⁺; the total amount of Si⁴⁺ and B³⁺ being 50-65%; 15-35% of La³⁺; 0-10% of Y³⁺; 0-8% of Gd³⁺, 0-5% of Yb³⁺; the total amount of La³⁺, Y³⁺, Gd³⁺ and Yb³⁺ being 25-45%; (Si⁴⁺+B³⁺)/(La³⁺+Y³⁺+Gd³⁺+Yb³⁺) is 1.7-2.3; 0.5-20% of Nb⁵⁺; 0-5% of Ti⁴⁺; 0-7% of Ta⁵⁺; 0-5% of W⁶⁺; the total amount of Nb⁵⁺, Ti⁴⁺, Ta⁵⁺ and W⁶⁺ being 0.5-20%; (Nb⁵⁺+Ti⁴⁺)/(Nb⁵⁺+Ti⁴⁺+Ta⁵⁺+W⁶⁺) being 0.7-1; (Nb⁵⁺+Ti⁴⁺+Ta⁵⁺+W⁶⁺)/(Si⁴⁺+B³⁺) being 0.01-0.35; (Nb⁵⁺+Ti⁴⁺+Ta⁵⁺+W⁶⁺)/(La³⁺+Y³⁺+Gd³⁺+Yb³⁺) being 0.04-0.4; 0-10% of Zr⁴⁺; 0.5-5% of Zn²⁺; 0-6% of Bi³⁺.
 10. The optical glass according to claim 9, also optionally comprising: Li⁺, Na⁺ and K⁺ in a total amount of less than 10%; and Ba²⁺, Mg²⁺, Ca²⁺ and Sr²⁺ in a total amount of less than 10%.
 11. The optical glass according to claim 10, wherein: the total amount of Li⁺, Na⁺ and K⁺ being less than 5%; and the total amount of Ba²⁺, Mg²⁺, Ca²⁺ and Sr²⁺ being less than 5%.
 12. The optical glass according to claim 9, wherein: 1.1-3% of Zn²⁺; 0-less than 2.5% of Gd³⁺; 0-less than 3% of Ti⁴⁺.
 13. The optical glass according to claim 9, wherein the composition is free of Ta⁵⁺.
 14. The optical glass according to claim 9, wherein the refractive index nd is 1.78-1.85, the Abbe number νd is 40-50, the corresponding wavelength is below 420 nm when the transmittance of glass reaches 80%, the density is below 5 g/cm³, and the upper limit of devitrification temperature is below 1250° C.
 15. A glass preform, which is made of the optical glass according to claim
 9. 16. An optical element, which is made of the optical glass according to claim
 9. 